Add a link to the OpenAPI schema where relevant

Fixes #329

docs/custom-actions.md

@@ -74,3 +74,5 @@ The program must finish within 15 seconds.
 If the `hook` defines an HTTP URL then this URL will be invoked as HTTP POST. The action is added to the query string, for example `<hook>?action=update`, and the user is sent serialized as JSON inside the POST body with sensitive fields removed.
 
 The HTTP hook will use the global configuration for HTTP clients and will respect the retry configurations.
+
+The structure for SFTPGo users can be found within the [OpenAPI schema](../httpd/schema/openapi.yaml).

docs/dynamic-user-mod.md

@@ -53,3 +53,5 @@ fi
 ```
 
 Please note that this is a demo program and it might not work in all cases. For example, the username should be obtained by parsing the JSON serialized user and not by searching the username inside the JSON as shown here.
+
+The structure for SFTPGo users can be found within the [OpenAPI schema](../httpd/schema/openapi.yaml).

docs/external-auth.md

@@ -54,6 +54,8 @@ else
 fi
 ```
 
+The structure for SFTPGo users can be found within the [OpenAPI schema](../httpd/schema/openapi.yaml).
+
 An example authentication program allowing to authenticate against an LDAP server can be found inside the source tree [ldapauth](../examples/ldapauth) directory.
 
 An example server, to use as HTTP authentication hook, allowing to authenticate against an LDAP server can be found inside the source tree [ldapauthserver](../examples/ldapauthserver) directory.

docs/post-login-hook.md

@@ -20,6 +20,8 @@ The program must finish within 20 seconds.
 If the hook is an HTTP URL then it will be invoked as HTTP POST. The login method, the used protocol, the ip address and the status of the user are added to the query string, for example `<http_url>?login_method=password&ip=1.2.3.4&protocol=SSH&status=1`.
 The request body will contain the user serialized as JSON.
 
+The structure for SFTPGo users can be found within the [OpenAPI schema](../httpd/schema/openapi.yaml).
+
 The HTTP hook will use the global configuration for HTTP clients and will respect the retry configurations.
 
 The `post_login_scope` supports the following configuration values: